Aims Pregnancy amongst under 16s has been reported to result in worse outcomes for the baby, including low birthweight. This study aimed to find out whether the under 16s need to gain more weight during pregnancy to avoid this outcome.

Method A retrospective case control study of pregnancy outcomes in girls delivering before the age of 16 and women delivering aged 25–30. Data was collected from medical case notes, including maternal age, pregnancy weight gain and infant birth weight.

Results Although weight gain amongst under 16s was similar to that in the control group, average birthweight of babies born to under 16s was less than in the older group. For both girls and older women greater weight gain in pregnancy did result in higher birth weights.

Discussion As younger girls are still growing it may be necessary for them to achieve a greater pregnancy weight gain in order to achieve a satisfactory birth weight.